1. Field of the Invention
The present invention relates to a rotary electric machine such as a vehicle AC generator, and particularly, to a terminal treatment structure of a stator lead conductive wire.
2. Description of the Background Art
As a generator provided on a vehicle, normally, a three-phase AC generator having a Lundell-type rotor is used.
In such an AC generator, on the stator side, three-phase stator coils are wound on a stator core, and the stator coil has a lead conductive wire. The end of the lead conductive wire has a metallic connection terminal attached thereon, and thereby is connected and fixed to a three-phase full-wave rectifier provided on a bracket.
A copper wire having an insulation coating with a high heat resistance, such as a polyamide-imide electric wire, is used for the stator coil. The lead conductive wire is formed by the copper wire extending from the stator coil. The connection terminal is formed by copper-based metal. Joining between the connection terminal and the lead conductive wire has been made as shown in Patent Document 1 (Japanese Laid-Open Patent Publication No. 2003-209944), for example.
That is, the connection terminal has a tube-shaped hole portion having no discontinuity, which is formed by rolling a copper plate into a circular-tube shape and joining its butting portions by welding using copper phosphorus brazing material. The lead conductive wire is inserted into the hole portion, and from the outside, pressure and current are applied to the connection terminal by an electrode, whereby fusing (pressure resistance welding) is performed. The temperature upon the welding increases up to about 1000° C. The circular-tube-shaped hole portion is flattened by the applied pressure and the temperature increase, and two lead conductive wires whose insulation coatings are carbonized are arranged in a row in the flattened hole portion. Thus, the two lead conductive wires are joined with the connection terminal.
As described above, upon the manufacture of the connection terminal, a copper plate is rolled into a circular-tube shape and its butting portions are joined into a circular-tube shape through brazing with copper phosphorus brazing material applied thereto. Upon the brazing, the copper phosphorus brazing material flows out from the butting portions of the connection terminal, whereby the copper phosphorus brazing material adheres on the inner circumference or the outer circumference of the circular-tube-shaped hole portion beyond a predetermined range, or the copper phosphorus brazing material adheres on a portion (torsional portion) having a low strength of the connection terminal. As a result, such a portion on which the copper phosphorus brazing material has adhered is hardened, so that the connection terminal becomes hard to be deformed.
In addition, the following problem arises. That is, in the state in which the copper phosphorus brazing material has adhered, when fusing is performed for the connection terminal and the lead conductive wire, a tin coating on the surface of the connection terminal or the copper phosphorus brazing material is melted into liquid metal by the fusing, and then a “liquid-metal embrittlement phenomenon” occurs in which the tin or the copper phosphorus brazing material in a liquid metal state diffuses on a metal body at a tensile-stress-applied portion (particularly, a torsional portion near the base of the connection terminal protruding from the circular-tube-shaped portion) of the connection terminal and thereby the metal body becomes brittle. As a result, a crack occurs at the moment when the metal body is cooled. In addition, if the copper phosphorus brazing material has adhered on the outer circumference of the hole portion of the connection terminal in a thick amount and over a wide range, a clearance in the shaft direction between the outer circumference of the hole portion of the connection terminal and a blade of a cooling fan facing to the outer circumference in the shaft direction becomes small. Then, if salt water or the like invades the clearance in the shaft direction, leakage current flows between the connection terminal and an end of the blade of the cooling fan, and electrochemical corrosion therebetween is promoted, whereby the connection terminal may be damaged.